. A laboratory guide in bacteriology, for the use of students, teachers, and practitioners. ingeing, they maydrop on the medium after removal of the stopper, andthus ruin a pure culture. 2. Hold the tube (or, if a transfer is made, bothtubes side by side) between the thumb and the fore-finger, so that the end of the tube rests on one edge ofthe hand (Fig. 27), holding them at an angle of about45°. If held horizontally, the condensation water,usually present at the lower end of the agar slant, willmoisten the surface and destroy a characteristic growth GENERAL BACTERIOLOGY 73 along the needle t
. A laboratory guide in bacteriology, for the use of students, teachers, and practitioners. ingeing, they maydrop on the medium after removal of the stopper, andthus ruin a pure culture. 2. Hold the tube (or, if a transfer is made, bothtubes side by side) between the thumb and the fore-finger, so that the end of the tube rests on one edge ofthe hand (Fig. 27), holding them at an angle of about45°. If held horizontally, the condensation water,usually present at the lower end of the agar slant, willmoisten the surface and destroy a characteristic growth GENERAL BACTERIOLOGY 73 along the needle track. If, held in a vertical position,contamination from the air may take place. 3. Remove the cotton stoppers by taking hold ofthe singed portion, and hold also by the singed partbetween the other fingers. If the portion of cottonfrom the inside of the tube is touched by the fingers, oraccidentally falls on the table or the floor, it becomescontaminated and must be singed before replacing. 4. Sterilize the straight platinum needle in theflame, holding it Uke a pendl. The platinum wire. Fig. 27Method of Inoculating Media should be heated until red hot, and the glass end passedslowly through the flame once or twice. 5. After cooling the needle by plunging into themedium, take up a small portion of a colony or cultureon the end of the needle by a lateral movement, and,when removing it from the tube, take care not to touchthe walls of the tube. If any cotton accidentally sticksto the mouth of the tube, it should be burnt off with ahot platinum needle, and then the mouth of the tubepassed through the flame before inserting the needle. 74 LABORATORY GUIDE IN BACTERIOLOGY 6. Insert the needle with the cxilture into the steriletube and draw along the surface of the slant, withoutpuncturing the jelly, and turn the needle during theoperation. 7. Replace the cotton plugs and sterilize the needlein the flame, as above. A stab culture is made by puncturing the mediumcentrally by a quick,
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